1. Field of the Invention
The present invention relates to laser diode arrays, and more specifically, it relates to microlens frames for laser diode arrays.
2. Description of Related Art
Laser diode arrays are used in a wide range of commercial, medical and military applications: materials processing (soldering, cutting, metal hardening), display technology/graphics, medical imaging (MRI) and surgical procedures (corneal shaping, tissue fusion, dermatology, photodynamic therapy), satellite communication, remote sensing, and laser isotope separation. In certain solid-state laser applications, it is desirable to use laser diode arrays to optically excite, i.e. "pump," the crystal hosts. Diodes offer a narrow band of emission (reducing thermal lensing), compactness, high electrical efficiency and higher reliability as compared to flash lamps. Despite these numerous advantages, however, diode-pumped solid-state lasers (DPSSLs) have gained slow market acceptance due to the high cost associated with the laser diode array pumps. Significant diode array cost reductions would enable wide deployment of DPSSLs and new architectures to be realized that were previously cost prohibitive. In particular, low-cost diode arrays would bolster the inertial confinement fusion (ICF) and inertial fusion energy (IFE) programs that require laser diode arrays in very high volumes.
Historically, much of the research and development in this area was devoted to solving diode material and fabrication issues in order to improve the yield and reliability of laser diodes. High quality InAlGaAs and InGaAsP laser diodes are now commercially available for pumping Nd:YAG at .about.810 nm. As much as 100 W/cm of peak power is possible under pulsed operation, and over 10,000 hours of continuous wave operation in commercial systems has been demonstrated at .about.30 W/cm. Although these types of performance improvements have led to cost reductions in the past, there has not been a complementary improvement in the packaging technology, which is now limiting further cost reductions from being achieved.
To date, most packaging/heatsink schemes use a "rack and stack" architecture. In this method, individual laser bars are fabricated into sub-assemblies, and the sub-assemblies are then bonded together to produce larger two-dimensional arrays. Labor intensive steps associated with handling individual components prevents the production of arrays in large volume and in high yield. To reduce manufacturing costs it is important to utilize a monolithic approach for mounting laser diode bars. Similarly, it is advantageous to be able to microlens a large number of laser bars simultaneously.